alpha coma
A comatose state with preserved alpha rhythm on EEG, typically indicating brainstem pathology.
Full Definition
Alpha coma is a specific EEG pattern observed in comatose patients characterized by the presence of widespread, non-reactive alpha frequency (8-13 Hz) activity that resembles normal awake alpha rhythm but lacks normal reactivity to stimulation. This pattern typically results from lesions in the upper brainstem, particularly the rostral pons, that disconnect the cortex from ascending arousal systems while leaving the thalamo-cortical alpha-generating mechanisms intact. Alpha coma generally carries a poor prognosis and is associated with conditions such as anoxic brain injury, drug intoxication, or brainstem infarction. The alpha activity is characteristically non-reactive to eye opening, auditory stimulation, or painful stimuli.
Usage
Usage note: Emphasize non-reactivity to distinguish from normal alpha rhythm in awake patients.
In Context
- "The comatose patient displayed alpha coma pattern with widespread non-reactive 10-Hz activity." — ICU EEG interpretation
- "Alpha coma was identified following anoxic brain injury, indicating poor neurological prognosis." — Neurological consultation report